When you see an item heavily discounted online, do you still have to look further or call in to see if there is a better price? the answer is a lot of the times YES.
On the popular items when there is a saving, it will mostly be matched by other retailers too, even on Prime day from Amazon, you may find similar pricing on other sites too.
there are exceptions to this and sometimes only one retailer will have those savings, some times others will have it on a different date in order to compensate from the manufacturer against that day when the competitor had a lower price, After all it is not only the retailer that is looking to gain money from a momentum that customers have and buy for the cheaper price, the vendor is mostly under these specials too.
My advice, even on prime day, you should still do a comparison to other retailers online or by phone.